Method of separating granular catalyst from a liquid



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States Patent M 2,924,590 "airmen or SEHARATING GRANULAR CATA LYST FROMA LIQUID nruce; Biriadi'chjihrtlsfill, one; assign'or to Phillips IPetroleum compan a corporation of Delaware j gimsiicaii'ali ia'hur 9,1956', Serial No. 558,082

9 Claims. or. 260-882) This inventionrelates toa method of separatinggranular catalyst froma liquid Heretofore, processes have been devisedfor producing olefin polymers in liquid phas'ein the presence ofasolvent and a .finel y divided catalyst. Such a process for producingpolymers having uhique characteristics is described in copehding,applications Serial No. 476,306, filed December '20, :1954, nowabandonedgbyJ. P. Hogan and R. L. Banks and Serial No. 496,515, filedMarch 24, 1955, by M. R.;Cines. i I accordance with this invention, thecatalyst is removed from a liquid reactidn emuem containing finelydivided catalyst by passing s ame th rough a fixed or moving b'edcatalytic reactorwherein the finely-divided particles areretained by thefixed or moving bed as the liquid passes .therethrough, This same bed issubsequently utilized tor the catalytic conversion of further quantitiesof fe ed whichis passed therethrojugh during aprocess cycle. Also, thefixed or movingbed catalyst is 'peridical lyregenerated, and theregeneration gases can be advajntageou'sly passed through the b'edatsuch velocity as to entrain and carry.away-fines ,deposite'cl on thefixedor movingbed during passage of the liquid reaction efijuenttherethrough. ,Ins'om'e instances, additional feed canbeadded to the'efilu'ent from the liquid phase cat- 51 ic reaction-before 'it'ispassed into the aforementioned cataly'st bed, in which case additionalproduct is formed atthe time the granular catalyst is removed by passageof the solution through'thec'atalyst bed.-

, ccor'din'gly, it isanobjectof the inventidn to provide a mprovedcatalytic process fo'r'fthe separation of granular 'c'atalyst'fioin aliquid reactioneffluent.

it, ;It is a further objectto utilize oneor more fixed bed reactors inconjunction with'a liquid phase cata ya raeq Itisa"still'fiiitherfobject to providean etficient and economical system for theremevaier granular catalyst from the efiluent of a liquid-phasepolymerization reobjects, advantages and features of the noon willbecome apparent from the following detailedjdescription. taken inconjunctionwith the accomf-P n i s d awin i which Th'e figure is a flowdiagram illustrating the system of 1t ti -..v 1

M "Referring now to the drawing in detail, the material etc She.c'onvertedis fed to ajliquidphase catalytic reactor 2110 through avalved line 11. A'granular catalyst enters wthe reactor through a line12 controlled by a star valve 1'3,"an'd this catalyst can be'adrnixedwith a solvent introv duced through a valved line 14 before .it 1 entersthe reeater. "Preferably and advantageously, the reactor is ided"vvithastirrer 15 driven by a motor 16.

"e efiluent'ffr'omthe reactor, containing the reaction dduct dissolvedin the solventtogetherwith the finely divided catalyst particles andsome 'imreacted feed, is passed through a line 17 to a vacuum flash unit18. From 2 this unit, the urir'eacte'd feed passes overhead throughaline 19 whence it passes to' a steam jet ejector 20 to which steam isapplied through a pipe 21. Cooperating with the ejector 20 is acondenser 22 from which water is withdrawn downwardly from a valved line23 and the unreacted material is taken overhead through a valved line24, for recycle if desired.

The bottoms product from the flash unit 18 is withdrawn by a line 25 andadmixed with additional quantities of solvent which are introducedthrough a valved pipe 26. This mixture then passes through a heater 27to a surge vessel 28 equipped with a stirrer 29 driven by a motor 30. Inthe heater and vessel, any product is dissolved which may have beendeposited onthe catalyst particles.

From the vessel 28, the mixture passes to one of; a plurality 31, 32 and33 of fixed bed catalytic reactors. These, reactors are provided,respectively, with valved inlet lines 31a, 32a and 33a which areconnected to a common discharge header 34 leading from the vessel 28 toadmit the mixture to the fixed bed reactors, as desired. A line 35branches from the line 34 to admit additional feed for admixture, incertain embodiments of the invention, with the effluent from the reactor10.

The reactors 31, 32 and 33 are further provided with inlet lines 31b,32b and 33b, respectively, which communicate with a common header'37 towhich feed can be introduced through a valved line 38 and solvent can beintroduced through a valved line 39. The reactors are also provided withthe respecitve sets 31c, 32c, 33c and 31d, 32d, 33d of lines which leadto a header 40 for withdrawing a product A from the reactors, asdesired, and a header 41 for withdrawing aproduct B.

A regeneration gas, such as oxygen-containing flue gas, can beintroduced to the reactors through a header 42 and a set 3 1e, 32a and332 of catalyst regeneration gas inlet pipes, the spent regeneration gasleaving through a set 31 32 33 of regeneration gas outlet pipes whichcommunicate with a common regeneration gas outlet header 43.

In operation, each of the reactors 31, 32 and 33 passes through threecycles of operation. In the first cycle, the

'effiuent fromvessel '28 passes through the reactor, and

the finely divided suspended catalyst therein is deposited upon thefixed catalyst bed. The converted material dissolved in solvent is thenwithdrawn through header 40 for treatment in any suitable manner toseparate the product from the solvent. At the end of this step, .it islines 38, 39 are introduced to the catalyst bed after shutting off theflow of mixture thereto from vessel 28. Thereupon, a catalyticconversion reaction takes place in the fixed bed to produce-a secondproduct which is withdrawn through header 41 and separated from solventin any suitable manner.

During the third cycle of operation, regeneration gas is admitted to thecatalyst bed to regenerate the catalyst, and the spent regeneration gasis withdrawn through the header 43. It is a feature of the inventionthat, during this regeneration step, the finest catalyst particle'sdeposited upon the bed during the passage therethrough of the mixturefrom vessel 28 are caught up in the gas stream and thus removed fromthe-system. Thus, by the system of the invention, no accumulation offines occurs in the catalyst bed.

As a further feature of the invention, additional feed material can beintroduced through the line 35 along with the mixture from vessel 28.This material is converted in the catalyst bed at the same'time thefinely di- Patented Feb. 9, 1960 vided catalyst is being taken out ofthe eifiuent mixture from reactor 10.

Those skilled in the art will understand that the reactors 31, 32 and 33are sequentially operated so that each of them, atany one time,is'passing through a different one of the, three operating cyclespreviously de* scribed. 7

As a specific embodiment of the invention, I will now describe a processfor the polymerization of ethylene by the method of the invention but itwill be understood that the process is applicable to various other typesof liquid phase catalytic conversion reactions, as well as thepolymerization of various types of olefinic materials as will be pointedout more fully hereafter.

' In the productionof polyethylene, the feed is ethylene of 95 percentpurity containing small quantities of methane, ethane and/or carbondioxide, and preferably treated to remove oxygen. This material is fedat a rate of 14.6 cubic feet per hour to the reactor together with onegallon per hour of isooctane solvent introduced through line 13 togetherwith suflicient chromium oxide on silica-alumina catalyst to maintain0.1 to 0.5, specifically 0.3 weight percent, catalyst in the efiluent.The reactor is operated at a temperature of 285 F. and a pressure of 500pounds per square inch gage, i.e., surficient to maintain a liquid phasein the reactor. The reactor effluent contains 0.3 weight percentcatalyst, 7.2 weight percent polyethylene, 7.2 percent ethylene, 0.7percent light gaseous impurities and 84.6 percent solvent.

The flash zone 18 is maintained at the same temperature as the reactor,and is operated at a pressure of 33 p.s.i.g. The effluent from the flashzone is essentially free from unreacted ethylene, and it is admixed withsolvent from the line 26 in a sufficient amount to provide a solutioncontaining 10 percent by weight of polymer. In the heater 27, thetemperature is raised to 335 F., at which temperature the materialenters one of the fixed bed reactors 31, 32 or 33. This heating causesthe solvent to dissolve olf'most of the polymer coating on the catalyst,and, in the agitator vessel 28, the hot solvent and polymer coatedcatalyst are intimately mixed, thereby substantially completely removingthe polymer from the catalyst. After passage of the mixture from vessel28 through the fixed bed, isooctane solvent from line 39 is passedtherethrough to wash off any polyethylene deposited on the fixed bedcatalyst.

Thereupon, ethylene feed and solvent are introduced through lines 38 and39. The fixed bedcatalyst is chrornium, oxide supported onsilica-a1umina and, during the reaction period, the polymerization takesplace at a temperature of 300 F., a liquid hourly space velocity of 3,and an olefin concentration of 3 weight percent under a pressuresufficient to maintain liquid phase conditions.

,'After the polymer is formed, it is removed or washed oif the catalystby isooctane solvent at a temperature of about 350" F., and theregeneration takes place with dry air diluted with inert gas, e.g., fluegas, at a temperature of about 950 F.

It will be understood that the specific operating conditionshereinbcfore given can vary to some extent depending upon the type ofproduct desired, and the nature of the olefin charge. The followingtable exemplifies the ranges within which the aforementionedvariablesmay be set.

Table Reactor 10 Temperature olefin polymerization 150 to 450 F.

Preferred temperature-ethylene 200 to 350 F. Preferredtemperature-propylene 150 to 250 F. Preferred temperatureethylene,propylene copolymer 240 to 320 R, preferably 250 to 280 F. PressureSufiflcient to maintain a liquid1 phase, preferably 500 Temperatureproduced by heat- Olefin concentration in feed ..r0.'1 to 40 weightpercent, preterably 0.5 to 10 weight percent. Contact time 2 minutes to10 hours preterably 30 to 300 m nutes. Flash zone:

Temperature Same or higher than reaction temperature. Pressure Notcritical, usually sub- 7 r atmospheric.- Eifluent Substantially free ofolefin.

Solvent added through line 26- Suflicient to provide polymer Iconcentration below 15 weight percent, preferably 5 to 10 weightpercent.

At least the melting point of polymer 250-400 F., preterably 275-350 F.

Fixed bed reactors:

Polymerization temperature- Preferred temperature for Preferredtemperature for 1 Pretflerrled tempelrature illor Pressure S fliclent tomaintain q phase. Feed rate 01-5108 PHSV, preferably 14 Olefinconcentration 0.1 10 weight percent, pref- 1 erably 2-4 weight percent.

Wash'temperature 300-400 F.

Regeneration temperature 900-1100 F.

It will be understood that the invention is not limite to ethylenepolymerization but can be very advantageously appliedto the productionof homopolymers or copolymers of l-olefins having. no more than 8carbon'atoms with no branching nearer. the double bond than the4-'position. For example, polymerization of propylene, l-octene and thelike, can be advantageously conducted, as well as polymerization ofdiolefins or conjugated diolefins of no more than 8 carbon atoms. 7

The polymerization catalyst can advantageously be chromiumoxidesupported on silica, alumina or silicaalumina. However,'various otherpolymerization catalysts can be used, and various materials, such asthoria and zirconia are suitable as supports and have catalyticactivity. Additional promoters such as zinc .oxide, magnesium oxide,strontium oxide, and the like can be employed. Also, various solventscan be'utilized provided that they do not impair the activity of thecatalyst. Thus aliphatic and alicyclic hydrocarbons of 3 to 12 carbonatoms preferably 5 to 12 carbon atoms per molecule are suitable,specifically propane, normal butane, cyclohexane, methylcyclohexane andisooctane.

While the invention has been described in connection with a present,preferred embodiment thereof, it is to be vunderstood that thisdescription is illustrative only and granular catalyst in suspension;passing said efliuent through a fixed bed of additional chromium oxidecatalyst whereby granular catalyst is deposited upon the fixed bed;passing additional l-olefin in solvent through the -fixed bed topolymerize said additional l-olefin; and subsequently passing anoxidizing gasthrough said fixed bed to remove carbonaceous depositsfromsaid catalyst.

2. The improvement of claim 1 wherein the fixed bed after deposition ofcatalyst is washed free of polymer by passing solvent free of polymer,monomer, and catalyst through said fixed bed prior to passing additionall-olefin insolvent through said fixed bed.

3. The improvement of claim 2 wherein the oxidizing gas is passedthrough said fixed bed at such a velocity as to suspend and carry awaythe most finely divided particles of said catalyst from said fixed bed.

4. The improvement of claim 2 wherein the l-olefin is a mono-l-olefin of2 to 8 carbon atoms and the said chromium oxide catalyst is supportedo'n an oxide selected from the group consisting of silica, alumina, andsilica-alumina.

5. The improvement of claim 4 wherein the l-olefin is ethylene.

6. The improvement of claim 4 wherein the l-olefin is propylene.

7. The improvement of claim 4 wherein the l-olefin is a mixture ofethylene and propylene.

8. The metho'd of producing polymers of l-olefin which comprises passinga hydrocarbon l-olefin of 2 to 8 carbon atoms in contact with ahydrocarbon solvent and a granular chromium oxide catalyst through afirst polymerization zone; removing an efiluent from said firstpolymerization zone comprising unpolymerized olefin, polymer, solventand granular catalyst in suspension having polymer dissolved thereon;vacuum distilling said eflEluent to remove unpolymerized olefin;adjusting the polymer concentration in the solvent to less than 15weight percent; heating and agitating the resulting solution to dissolvepolymeric material deposited on catalyst; passing the resulting mixturethrough a fixed bed of additional chromium oxide catalyst whereby thegranular catalyst suspended in the solvent is deposited on said fixedbed; and passing additional l-olefin of 2 to 8 carbon atoms in solventthrough the fixed bed to polymerize said additional l-olefin.

9. In the polymerization of hydrocarbon l-olefins in liquid phase in ahydrocarbon solvent and in contact with a granular chromium oxidecatalyst, the improvement comprising passing said olefin, solvent andgranular catalyst through a first polymerization zone; removing aneffluent from said polymerization zone comprising solvent having polymerdissolved therein along with said granular catalyst in suspension;passing said efiiuent through a fixed bed of additional chromium oxidecatalyst whereby granular catalyst is deposited upon the fixed bed; andpassing additional l-olefin in solvent through the fixed bed topolymerize said additional References Cited in the file of this patentUNITED STATES PATENTS 2,018,507 Alton Oct. 22, 1935 2,617,709 CornellNov. 11, 1952 2,702,288 Hoeksema et al Feb. 15, 1955 2,726,234 Field etal Dec. 6, 1955 2,728,754 Evering et a1 Dec. 27, 1955 2,731,452 Field etal Ian. 17, 1956 OTHER REFERENCES Perry: Chemical Engineers Handbook(1950), page 968 (Granular Beds), McGraw-Hill Book Company, New York.

1. IN THE POLYMERIZATION OF HYDROCARBON 1-OLEFINS IN LIQUID PHASE IN AHYDROCARBON SOLVENT AND IN CONTACT WITH A GRANULAR CHROMIUM OXIDECATALYST, THE IMPROVEMENT COMPRISING PASSING SAID OLEFIN, SOLVENT ANDGRANULAR CATALYST THROUGH A FIRST POLYMERIZATION ZONE, REMOVING ANEFFLUENT FROM SAID POLYMERIZATION ZONE COMPRISING SOLVENT HAVING POLYMERDISSOLVED THEREIN ALONG WITH SAID GRANULAR CATALYST IN SUSPENSION,PASSING SAID EFFLUENT THROUGH A FIXED BED OF ADDITIONAL CHROMIUM OXIDECATALYST WHEREBY GRANULAR CATALYST IS DEPOSITED UPON THE FIXED BED,PASSING ADDITIONAL 1-OLEFIN IN SOLVENT THROUGH THE FIXED BED TOPOLYMERIZE SAID ADDITIONAL 1-OLEFIN, AND SUBSEQUENTLY PASSING ANOXIDIZING GAS THROUGH SAID FIXED BED TO REMOVE CARBONACEOUS DEPOSITSFROM SAID CATALYST.